This invention relates to cooking or kitchen ventilation systems and, more particularly, to an improved ventilation system of this type for use in various commercial and institutional establishments.
In commercial and institutional cooking kitchens, restaurants and fast food service establishments, a powered exhaust system commonly is used to remove the cooking fumes from the kitchen for discharge to the outside atmosphere. A hood in the kitchen generally overlying the particular cooking appliances collects the fumes, and an exhaust duct from the hood in turn typically extends upwardly within the building structure to an outside outlet higher than the hood. A blower commonly provides negative pressure in the duct for forced venting of the kitchen air and fumes from the hood and through the exhaust duct.
Because of the need to be concerned with increasingly stringent fire regulations and the desire to increase safety and efficiency, these so-called kitchen ventilation systems have become increasingly technically complex, requiring painstaking and scientific design during which many parameters, specifications, concerns and hazards must be kept in mind by the design engineer.
The possibility of fire is a most important hazard to be addressed because of the presence of grease, smoke gases, volatiles and other flammable substances rising from the cooking area or carried upward into the ventilation, in view of the cooking heat or even open flames from cooking. Consequently, a fire damper is often required to be installed in the duct system, the damper being held open by a heat fusible link and closed by a weight or spring when the link is melted. Fire dampers are seldom operated on a regular basis, so that the grease-laden air can bind the damper journals, linkages and other parts to prohibit closing of the damper, as by the action of a weight, if there is a fire.
Another problem of prior art damper arrangements is that if the damper stays open at all times, even when the exhaust blower is off at night, for example, a strong chimney effect can produce loss of significant heat energy, especially in colder climates as heat escapes from the heated building out the open duct.
Manually operated dampers have also been used but usually are not operated regularly and properly over extended periods and if configured to be closed, for example, by a spring or weight in the event of a fire, are prone to failure just like other fire dampers.
For example, a conventional system long used in the industry is typified by the Graswich et al U.S. Pat. Nos. 2,961,941 and 2,971,452 where the damper is manually opened and spring closed. Various release means are described including manually activated, fire activated, and/or electrically activated means to shift a link so that the damper could be spring closed; but manual effort is required to open the damper. In practice, it is rare indeed when such a damper is opened and closed on a regular daily basis, particularly where there are many such damper systems in a single commercial place of business or institution.
A later system is typified by Gaylord U.S. Pat. No. 3,785,124 which utilizes a similar operating mechanism for the so-called make-up damper but which further employs a fresh air damper which is motor opened and spring closed. A limit switch secured adjacent the motor drive is tripped upon the damper being opened fully to deenergize the motor and simultaneously to energize a brake for holding the damper opened. To close the damper, the brake is released and a spring hopefully closes the damper against fixed stops.
Vandas U.S. Pat. No. 4,066,064 discloses an improved arrangement providing for powered opening and closing of the damper with a cylinder operated by water under pressure. This has certain advantages since the damper is opened and closed under power and provision can be made for using the cylinder to open and close the damper daily. This further allows for the tie-in of a fire control system to the same damper which, because of its frequent opening and closing, provides increased assurance that the damper will work in the event of a fire. However, a problem of this system has become evident in cold climates where the downdraft of freezing air within the open duct system can easily freeze the water in the cylinder and/or water lines. This, of course, renders the system inoperative while posing also the risk of rupturing the water lines connected to the actuating cylinder. If there is a multiple ventilator system with multiple actuating cylinders, all operated from a single source of water pressure, the rate of operation of the various cylinders can be different. Another disadvantage is that each such hydraulic cylinder has to be made of durable materials that will resist liquid leakage, heat and corrosion. The system of this patent also requires costly control valving.
Apart from the above, additional problems exist with known damper arrangements. For example, the hood opening typically is defined in wall structure lying in a near vertical plane and, in the usual arrangement, the damper when opened is pivoted about a horizontal upper damper edge, opening into the interior of the hood. Consequently, air exhausted through the hood opening necessarily is passed over the damper itself and grease coats the exposed outer face of the damper. Resultant fouling of the outside surface with grease is itself objectionable, but a more serious problem is that to close the damper, it has to be moved against the direction of the exhausted air moving through the rather restricted hood opening. Even if the blower were deenergized before closing the damper, the inertia, chinmey effect, etc. could yet impose a large force on the damper tending to keep it open. Because of this, the damper closing spring or power cylinder must be designed to be powerful enough to be certain to overcome the possible airflow forces.
A further drawback typically has the actuator extended when the damper is opened and exposed to the exhausted air. This means that in time the exposed operating mechanism can become grease coated and bound, and a cause of malfunction. This would be true, for example, with the power cylinder used in the ventilator arrangement disclosed in Vandas U.S. Pat. No. 4,066,064 which cylinder has an extended piston rod which is exposed to the exhausted air, and thus, may become grease coated and sticky with consequent risk of failure to retract.
An object of the invention is to provide an improved extraction unit for a so-called kitchen ventilating system of the type providing for venting of cooking gases, etc. by interconnection with an exhaust duct communicating to the atmosphere exterior to the kitchen, and useful in myriad industrial, restaurant, fast food and in institutional cooking applications.
It is an object, of the invention to provide such a an extraction unit having a damper which is power actuated for being quickly, easily and reliably opened or closed on periodic intervals, for example, daily, and preventing, when closed, wasteful escape of heat up the exhaust duct.
Another object of the invention is to provide such an extraction unit in which the damper is oriented and pivotally disposed for closing in the direction of air flow through the ventilating system; and, contrariwise, opening into the air flow.
It is a related object of the invention to provide such an extraction unit system in which the damper, when opened, conceals and protects the actuating mechanism to keep grease-laden air and gases from contacting the actuating mechanism; it being also an object of the invention to provide for the actuating mechanism to be in a contracted configuration when the damper is opened so that the actuating mechanism is intrinsically not prone to being fouled, coated with grease, or otherwise interferred with, while the damper is open.
Another object of the invention is to provide such a an extraction in which the damper is electrically actuated but which obviates the need for limit switches, external stops, and other devices which would otherwise be needed to limit movement of the damper.
A further object, of the invention is to provide such an extraction unit system in which the electrically-powered actuating mechanism is provided with sufficiently high operating power and leverage to provide not only rapid but forceful operation of the damper.
It is an object of the invention to provide such a an extraction unit which provides protection during the damper actuating to minimize damage and to prevent injury of persons or objects trapped between the damper and the adjacent structure.
Yet another object of the invention is the provision of such an extraction unit in which the movement of air through the system is accomplished so as to extract grease, grease particles and the like from the air moving through the ventilating system and to preclude the moving air from picking up and carrying the grease, particles, etc. up the exhaust duct.
Another object of the invention is the provision of such a kitchen ventilating system including a novel extraction unit, which provides automatic detergent-and-water washing of the interior of the extraction unit to wash out grease, deposits, and so forth on a daily basis, it being also an object of the invention to provide such a system which carries out water spraying within the extraction unit in the unlikely event of a fire.
Still other objects of the invention include the provision of such a system which is readily usable in any of a wide variety of industrial, restaurants, fast food and institutional cooking applications from large through small; which is extremely well suited to the expansion of kitchen facilities by adding more ventilating systems; which can be used equally well in single or multiple ventilation installations; and which can be designed in an extremely wide range of widths dependent upon the type of installation desired.
Other objects and features will be in part apparent and in part pointed out hereinbelow.